My dog has somewhat of injured leg what should i do.?

My dog got hurt a while ago on his right leg and healed after several weeks and since that day hes had a weak leg and when i played with him months after he got hurt again and couldnt walk properly for about 2 days and it later got slightly better and is doing fine now, but now i believe its his knee that i hear cracking while he walks like its kinda grinding on his bone or something it doesn't do it all the time though. Other than recommending going to the vet cuz we will if it doesn't heal, should i bring him for walks again cuz im just worried it gets worse hes reseted on it for a while now what do you think?? My dad wants me to exercise it is he right.